Goto the GPS tab
Click on the "Sat. Info" button
Check the DOP numbers.
Also, do you have a 2-D or 3-D fix (right side of tab)
If the PDOP value is > 8, then you aren't receiving very good satellite signals.
If possible, next time this happens, take a screenshot of the page and post. The page also shows Satellite signal strengths and position.
Rick - WA7VLMTP3-8, TPNA9, SA2006/7/9+/10, XMap 5.2/7.0 Pro, PN-20, PN-40, PN-60wSE & SPOT
For more Information, check out http://www.gps-wiki.com